/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.engine.iterator;

import org.apache.jena.atlas.io.IndentedWriter;
import org.apache.jena.atlas.lib.Lib;
import org.apache.jena.sparql.engine.ExecutionContext;
import org.apache.jena.sparql.engine.QueryIterator;
import org.apache.jena.sparql.engine.binding.Binding;
import org.apache.jena.sparql.procedure.Procedure;
import org.apache.jena.sparql.serializer.SerializationContext;

/**
 * QueryIterator for a procedure. Delays first touch until first call because first
 * touch may cause work to be done.
 */

public class QueryIterProcedure extends QueryIter1 {
    private final Procedure proc;
    private boolean initialized = false;
    private QueryIterator procIter = null;

    public QueryIterProcedure(QueryIterator input, Procedure proc, ExecutionContext execCxt) {
        super(input, execCxt);
        this.proc = proc;
    }

    private void init() {
        if ( !initialized ) {
            procIter = proc.proc(getInput(), getExecContext());
            initialized = true;
        }
    }

    @Override
    protected void closeSubIterator() {
        // Ensure initialized even if immediately closed.
        init();
        procIter.close();
    }

    @Override
    protected void requestSubCancel() {
        if ( procIter != null )
            procIter.cancel();
    }

    @Override
    protected boolean hasNextBinding() {
        init();
        return procIter.hasNext();
    }

    @Override
    protected Binding moveToNextBinding() {
        init();
        return procIter.nextBinding();
    }

    @Override
    protected void details(IndentedWriter out, SerializationContext sCxt) {
        out.print(Lib.className(this));
        out.print(" ");
        proc.output(out, sCxt);
    }
}
